There is prior art of long standing in the manufacture of such terminals, embodied in a wide variety of connecting means, for example in a simple junction block enabling connection of electrical wires, a switch or any other small electrical apparatus.
Since the terminal screw of such terminal is generally made to engage by screwing, with or into the connecting part within the insulating housing containing all or part of the connecting means, it is not possible to insert a closed tongue between the clamping plate and the connecting part of the connecting terminal without having beforehand completely unscrewed the screw, to lift it up, and thus created a passage for the closed tongue.
Such complete unscrewing of the screws entails the risk of loss of one or more screws if no precautions are taken to avoid same.
The risk of loss is not limited only to the case of installing closed tongue terminals, as for convenience one tends to use the same connecting terminals for open-tongue wire terminals, closed terminals and wires and consequently it is possible to inadvertently unscrew and lose a screw when merely installing an open wire terminal or a wire. Experience shows that this risk increases as the size of the connecting terminals decreases.
Meanwhile, the technological trend is for miniaturization of the components making up such screw terminals and the connecting means in which they are comprised, and for reduction of the manufacturing costs associated with said components, and likewise of the cost of assembly by the manufacturer and of implementation by installers.